Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to a disk drive suspension having different impedance values for its read conductor circuit and its write conductor circuit.
2. Description of the Related Art
Typically a disk drive suspension comprises a steel load beam having a base section, a spring section and a rigid section. The suspension also typically includes a flexure supported on the load beam that may comprise a laminate of a support metal such as stainless steel with a plastic film that support a slider incorporating a read-write head, referred to herein as a slider. The flexure may extend substantially the full length of the load beam rigid section and support one or more sets of conductive traces that connect the read or write heads of the slider to the suspension electronics at the base section of the load beam. Construction of the flexure laminate is either additive in the sense that the several layers of metal, insulative film and trace conductors are built up on one another, or subtractive in the sense that a full laminate is reduced in one or more areas to fewer than all layers.
In either case the insulative film between the metal layer, or between the load beam if there is no laminate metal layer, and the conductive traces is the same thickness under the conductive read traces as under the conductive write traces. As set forth hereinafter there are disadvantages to the same thickness of film at the read circuit conductors as at the write circuit conductors, especially in blocking achievement of a different impedance for these circuits.
It is an object of the invention, therefore, to provide greater control of impedance values in a disk drive suspension. It is a further object to provide a differential in impedance between read and write circuits in a disk drive suspension. It is a further object to provide a controlled thickness in the film insulative layer in the suspension flexure, differentiated between the read and write circuits, to vary the circuit capacitance and thus the impedance to optimize the impedance values for each circuit without compromise of the other circuit impedance. A further object is to provide a novel form of flexure for a disk drive suspension.
These and other objects of the invention to become apparent hereinafter are realized in a flexure for use with a load beam, the flexure comprising a metal layer (that will typically be adjacent to and fixed to a load beam), plural sets of trace conductors, and a plastic insulative film layer that serves to space the trace conductors from the metal layer in capacitance determining relation, the film layer having transversely to its longitudinal axis a differential thickness ranging from a lesser thickness in a first lateral portion adjacent one edge margin of the metal layer to a greater thickness in a second lateral portion adjacent the other edge margin of the metal layer, the plural sets of trace conductors including a first set of trace conductors defining a read circuit and attached to the film first portion at a spacing to be relatively closer to the metal layer across the film layer and a second set of trace conductors defining a write circuit and attached to the film layer second portion at a spacing to be relatively farther from the load beam across the film layer, whereby there is a capacitance differential between the read and write circuits, the capacitance differential providing the selected and different impedances for the circuits.
In a further embodiment, the invention provides a disk drive suspension having selected and different impedance values for its read trace conductor circuit and its write trace conductor circuit, the suspension comprising a steel load beam having a rigid section and extended along the length of the load beam rigid section a flexure for supporting a slider at the distal end of the load beam for operative association with a disk, the flexure comprising an assembly with the load beam of plural sets of trace conductors and plastic insulative film that spaces the trace conductors from the load beam in capacitance determining relation, the film having transversely of the load beam longitudinal axis a differential thickness ranging from a lesser thickness in a first lateral portion adjacent one edge margin of the load beam to a greater thickness in a second lateral portion adjacent the other edge margin of the load beam, the plural sets of trace conductors including a first set of trace conductors defining a read circuit and attached to the film first portion at a spacing to be relatively closer to the load beam across the film and a second set of trace conductors defining a write circuit and attached to the film second portion at a spacing to be relatively farther from the load beam across the film, whereby there is a capacitance differential between the read and write circuits, the capacitance differential providing the selected and different impedances for the circuits.
In these and like embodiments, typically, the selected impedance for the write circuit is greater than the selected impedance for the read circuit, the selected write circuit impedance ranges from 80 to 110 ohms, and the read circuit impedance ranges from 60 to 80 ohms.
Moreover, typically, the film first lateral portion has a thickness of not less than 0.00030 inch, and the film second lateral portion has a thickness of not less than 0.00050 inch, the film first and second lateral portions differing in thickness by at least 0.00020 inch, the differential thickness in the film first and second lateral portions continues for substantially the full length of the load beam rigid section, the flexure further comprises a steel layer opposite the load beam and bonded to the plastic insulative film, the plastic insulative film comprises polyimide resin, and the stiffness of the load beam is reduced less than about 10% as a result of the difference in thickness between the film first and second lateral portions.
In its method aspects, the invention provides a method of providing a flexure for a disk drive suspension comprising a steel load beam, the flexure comprising a stainless steel layer, an insulative film layer and sets of read and write conductor circuit defining trace conductors spaced from the steel layer by the film with selected and different impedance values for its read trace conductor circuit and its write trace conductor circuit, the method including maintaining a thickness differential between first and second laterally adjacent portions of the insulative film in capacitance determining relation, whereby there is a capacitance differential between the read and write circuits, the capacitance differential providing the selected and different impedances for the circuits.
In particular embodiments, the method further includes forming the insulative layer at a first substantially uniform thickness across the laterally adjacent portions, and thereafter selectively reducing the film thickness in one or the other of the portions to realize the desired capacitance values, or, initially forming the insulative layer at different thicknesses in respective laterally adjacent portions as by building up a polyimide layer in one area while masking the adjacent area to realize the desired capacitance values, selecting as the impedance for the write circuit an impedance greater than the selected impedance for the read circuit, selecting a write circuit impedance in the range of 80 to 110 ohms, and for the read circuit an impedance in the range of 60 to 80 ohms, and selecting for the film first lateral portion a thickness of not less than 0.00030 inch, and for the film second lateral portion a thickness of not less than 0.00050 inch, having the film first and second lateral portions differ in thickness by at least 0.00020 inch, and attaching the flexure to a load beam.